Lonnie David Franklin Jr. was on probation when voters passed Prop. 69 requiring offenders to submit DNA samples. By the time L.A. County got the equipment, he was no longer being supervised.

Authorities missed an opportunity years ago to catch the suspected Grim Sleeper serial killer before a final victim was slain, because his DNA was never collected as required under a 2004 law, according to interviews and records reviewed by The Times.

Lonnie David Franklin Jr.'s genetic profile was supposed to be added to the state's DNA databank of offenders because he was on probation for a felony when voters approved Proposition 69, a sweeping expansion of the state's DNA collection.

The Los Angeles County Probation Department was given the task of obtaining DNA samples from tens of thousands of local offenders who were on probation when the law went into effect in November 2004.

But by the time the agency began collecting DNA, Franklin was no longer under its supervision. Thousands of other offenders may also have avoided providing a sample during the same period, officials said.

More than a year later, the Grim Sleeper struck again.

A homeless man found the body of Janecia Peters on South Western Avenue on New Year's Day 2007. The 25-year-old had been shot and covered with a garbage bag. DNA tests helped link her killer to other slayings by the Grim Sleeper dating back to the 1980s.

Her mother, Laverne Peters, said the failure to collect Franklin's DNA reinforced her belief that authorities could have done more to catch the serial killer sooner and prevent her daughter's death.

"Her life could have been possibly saved," Peters said. "That's the part I'm going to think about a lot — if only."

Franklin, 57, was charged last week with 10 murders committed during two separate periods. The first, between 1985 and 1988, claimed the lives of seven women.

The next period began in 2002 with the slaying of 15-year-old Princess Berthomieux. A year later, the body of Valerie McCorvey, 35, was discovered in the Westmont area. DNA collected from the crime scenes linked those two slayings to one of the earlier killings.

The California Department of Justice compares DNA from unsolved cases against its database of offenders once a week, resulting in an average of 300 to 400 cold hit matches each month. But the comparisons never produced a match for the Grim Sleeper killings.

In 2007, the LAPD created a task force of detectives to work exclusively on the crimes. The team painstakingly followed lead after lead, sometimes using unconventional tactics in an effort to solve the killings. At one point, police collected DNA samples from men arrested for soliciting prostitutes in the hopes of finding a genetic match to the assailant.

In the end, Franklin was arrested after a "familial" search of state DNA records indicated that a convicted felon was probably related to the killer. Franklin is the felon's father.

LAPD Det. Dennis Kilcoyne, who heads the department's task force, said police could have linked Franklin to the crimes sooner had his genetic sample been in the state's DNA databank. But he said detectives need to focus on the facts, not dwell on what might have been.

"It's tragic all the way around," Kilcoyne said, "but we can't change it now."

The opportunity to obtain Franklin's DNA was missed in the months it took law enforcement agencies to prepare to collect a huge volume of genetic samples under the 2004 law.

Proposition 69 applied to an array of offenders, including those convicted of any felony after the law passed and those who were on probation for a felony conviction. When the law was approved, Franklin was still serving three years of formal probation after his 2003 conviction for receiving stolen property, a felony.

Guidelines published by the California attorney general's office in March 2005 said probation departments were to collect samples from offenders then under their supervision.

A senior Los Angeles County probation official said it took the state and county time after the law's approval to come up with a plan to fulfill the new requirements. He said the probation department did not have the resources to immediately begin collecting samples and could not start until the agency obtained the necessary equipment and trained its employees.

The delays meant that probation officers did not start collecting DNA until late August 2005. Six weeks earlier, a judge changed Franklin's status so that he was no longer being supervised by a probation officer.

"We [did] not have authority over him," Dave Leone, the probation department's acting deputy director for field services, said.

Leone said that once the necessary equipment was in place his agency aggressively pursued offenders under probation. The department, he said, obtained samples from more than 54,900 offenders.

Leone said it is unclear exactly how many probationers avoided providing a sample because they were no longer under the agency's supervision when DNA collection began. But he estimated that about 13,000 offenders had their probation terminated between November 2004 and August 2005 without giving a swab.

"It's a sad situation," Leone said. "We just need to keep collecting DNA, and hopefully something like this will never happen again."

Rockne Harmon, a retired Alameda County prosecutor and an expert on DNA evidence, said the Grim Sleeper case highlights the need for a robust DNA database of criminal offenders to help solve other crimes.

Although Franklin was no longer on supervised probation after July 2005, he did remain on unsupervised probation for several months. Harmon said that meant he was still legally required to provide a DNA sample if asked.

But Harmon cautioned that many counties had difficulties obtaining DNA from unsupervised offenders on probation as they scrambled to comply with the new law.

"It's a huge logistical challenge," he said. "I have a feeling that this guy would have fallen through the cracks in many places."